There's only one global scope, but
there can be many different local scopes.
var myvar = 10; // a global myvar
function func1 () {
var myvar = 20; // a myvar which is local to func1
}
function func2 () {
var myvar = 30; // a myvar which is local to func2
}
function func3 () {
var myvar = 40; // a myvar which is local to func3
}
In this code fragment, there are four separate myvar variables. One is global, the other three are all local to their own functions.